1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device, particularly a method for manufacturing a semiconductor device using a high-density plasma apparatus in a manufacturing step of a semiconductor element (device) such as a thin film transistor.
2. Description of the Related Art
In recent years, a technique for forming a thin film transistor (TFT) by using a semiconductor thin film (a thickness of around several nanometers to several hundred nanometers) formed over a substrate having an insulated surface such as glass has been attracting attention. The thin film transistor is broadly applied to semiconductor devices such as an IC and an electro-optic device. In accordance with demands for a more compact and much higher performance semiconductor device, a development of a much higher performance thin film transistor having a minute structure is required. In order to manufacture a much higher performance and more compact thin film transistor, a gate electrode, a source wiring and a drain wiring, and the like with much higher reliability are required to be manufactured. For example, reliability of a TFT is improved by forming a protective film over a surface of a gate electrode to improve a heat resistant property of the gate electrode (For example, Patent Document 1).
[Patent Document 1]
Japanese Patent Application Laid-Open No.: H6-13615
As described in Patent Document 1, a nitride film such as a titanium nitride (TiN) film is formed over a gate electrode, and a source wiring and a drain wiring by a sputtering method, and a heat resistant property of the gate electrode, and the source wiring and the drain wiring is improved and oxidation is prevented. However, since the nitride film formed by a CVD method or a sputtering method has a defect inside the film and film quality is not sufficient, there is a concern that reliability of a TFT be lowered.